graphviz is a set of graph drawing tools for Unix or MS-Windows
(win32), including a web service interface (webdot).  Graph
drawing addresses the problem of visualizing structural information
by constructing geometric representations of abstract graphs and
networks. 

The goal of graphviz has been twofold: 

    to find efficient algorithms for making very readable
    drawings of graphs up to several hundreds of nodes,
    approaching the quality of manual layouts (made
    with CAD tools).  The algorithms should scale even
    further, as layout of large graphs can also offer
    a gestalt view of complex systems.

    to create convenient graph drawing systems and web
    services. This means defining useful interfaces and
    features to support applications.
